stratification是什么意思

　　Stratification in polar water normally is weak and transient.

　　極地水域的成層性是微弱而暫時的。

　　Stratification in polar waters normally is weak and transient.

　　極地水域的成層性是微弱而暫時的。

　　The stratification of beach deposits has been studied particularly.

　　對海灘沉積物的層理進行了著重研究。